The present disclosure relates to a controller and a control method for a wastegate. The wastegate is provided in a bypass passage that allows exhaust gas to bypass the turbine wheel of an exhaust turbine-type forced-induction device.
As described in Japanese Laid-Open Patent Publication No. 2015-214935, some of the controllers for wastegates of exhaust turbine-type forced-induction devices control a boost pressure of the engine by performing feedback control in which the operation position of the wastegate detected by a sensor is a control amount and the drive force of the wastegate is an operation amount.
The feedback control of the operation position produces detection errors in the sensor that detects the operation position and errors resulting from machining tolerances of the wastegate or components of the actuator. In particular, in a high-boost region, slight differences in the operation position of the wastegate cause the boost pressure to vary to a large extent. This makes it difficult to ensure the control accuracy of the boost pressure in the feedback control of the operation position.
Thus, in some cases, the conventional controller is unable to properly control the operation of the exhaust turbine-type forced-induction device depending on the running state of the engine.